We’d all like to enjoy the benefits of power steering, but with none of the weight or horsepower draw, right? Since that’s not possible, the next best thing is to find a pump that is light and powerful enough to do the job without draining too much power from the engine.
We caught up with KRC Power Steering, a company that has been designing and manufacturing power steering and serpentine pulley systems since 1997. KRC recently invested in first-of-its-kind testing equipment from Chant Engineering in New Britain, Pa., to further develop power steering pumps for racing applications.
A sophisticated one-off machine, it reveals that as engine speed increases in 1,000-rpm increments, one power steering pump can consume twice the power of another. The new findings could provide an edge to teams that need power steering, but also are looking for even the slightest horsepower gains.
“This custom-made machine records horsepower, flow and pressure, and checks the data every 1,000 rpm, from 1,000 to 10,000 rpm,” says KRC President Ken Roper. “It even produces graphs and retrieves information we didn’t request! But perhaps its most valuable attribute is that it reveals information we never knew before, like power consumption under load, and it validates everything.”
Surprisingly, the tester further confirmed that a small 5.9 cc pump is capable of developing as much flow as a bigger pump while consuming half the horsepower. During recent tests with several GM-style power steering pumps modified for competition, the tester demonstrated they absorb around 3.6 hp at 8,000 rpm. By comparison, KRC’s Pro Series 5.9 cc pump used on Aston Martin’s victorious Le Mans sports cars absorbs 1.9 hp. All pumps were tested with 125 psi of load applied, which is the average pressure generated in a power steering system when operating in the straight-ahead position.
The tester not only measures pressure and flow and calculates power consumption, but it also duplicates the data acquired on a racing lap. By providing KRC with the relevant data acquisition — operating pressures and flow referenced to rpm — they can feed the information into the tester and calculate horsepower consumption on each lap. Better still, if the data acquisition is synchronized with a GoPro video camera, pressures, flow, tire and steering loads, horsepower consumption etc., are all recorded and can be visually identified at any given position on the track.
For example, suppose a racecar is at its most deficient in a given turn, with data showing, say, 500 psi of pressure and 2.3 gallons per minute of flow, equating to consumption of 4 hp. However, such deficiencies might easily be corrected by simply using a different pulley diameter. Moreover the tester also checks the data over endurance race distances, monitoring heat generated within the power steering system.
The test equipment has demonstrated that the power steering system’s greatest efficiencies are achieved when the pump is operating between 3,000 and 5,000 rpm. It follows that if an engine operates mostly at 8,000 rpm, the power steering pump would function most efficiently at around half engine speed. You just need the appropriate pulley.
Compared with electric power steering, hydraulic power steering pumps can exhibit a great deal of feel by providing accurate feedback of forces acting upon the front wheels. Nonetheless, hydraulic pumps are designed to provide adequate flow when the engine is idling. As a result, the pump often moves more fluid than necessary when the engine is operating at faster speeds.
KRC managed to retard flow rates with increasing engine rpm. As a result, “feel” qualities are preserved even as engine rpm rises. KRC can tailor the feel for different drivers by offering optional flow valves. These flow-control valves work like jets in a carburetor. Different orifices regulate fluid transfer. Those marked B, C, D, or E, increase flow rate up to 12 liters per minute in one-liter increments. The higher letter indicates greater hydraulic assistance but less feel. In contrast, flow valves marked with numbers 4, 5, 6, and 7 provide less assistance but greater feel. Simply select the flow valve that gives you the correct steering feel.